Secondary emission tube ring circuit



June 27, 1950 R. B. TROUSDALE 1 84 SECONDARY EMISSION TUBE RING CIRCUITFiled Sept. 1, 1948 /6 SOURCE OF TRIGGER- IMPULSES A A A A A A A A B C &U L

F76. 2 D L f f F k INVENTOR.

ROBERT E. TROUSMLE ATTORNEY Patented June 27, 1950 2,512,934 SECONDARYEMISSION TUBERINQ CEECULT Robert B. Trousdale, Rochester, N. Y.,assignor to Strombe'rg-Carlson Company, a corporation of New YorkApplication September 1, 1948, Serial No. 47,305

4 Claims.

This invention relates to counting circuits and more particularly toclosed-ring pulse counting circuitsincluding a plurality of stages ofelectron discharg e devices of the secondary emission type.

Objectsand advantages of my invention w11l be apparent from thefollowing description when read in conjunction with the drawings inwhich FigQ l is a schematic diagram of a three-stage closed-ring pulsecounting circuit and Fig. 2 illustrates/in diagrammatic form varioustypical operating conditions found in the circuit shown in 'Fi fi.

Referring to the drawings, there is shown a closed-ring pulse countingcircuit comprising a plurality of stages. In the illustrated embodimentof my invention three stages are shown, although any number of stagesmay be utilized, it being simply. necessary to join the output of thelast stageto the input of the first stage.

The three stages shown include electron discharge devices l, H and 23,respectively, of the secondary emission type such as those described inSkellett Patent 2,293,177 wherein there is disclosed a vacuum tube orelectron discharge device which may be substantially instantaneouslyenergiz'ed or de-energized according to its initial condition. Eachdevice comprises a plurality of electrodes'including a cathode electrode2, an input'control electrode or grid 3, and a primary or first anode 4,the cathode and the first anode constituing a pair of electrodes betweenwhich a primary stream of electrons may be established. The controlelectrode 3 is effective in controlling the primary stage. Means is alsoprovided for establishing a secondary electron stream within thedischarge device including a secondary electron emitting electrode ordynode 5, a collector electrode or grid 8 for collecting secondaryelectrons'released by the dynode when the primary electrons passingthrough an aperture in the first anode l bombard the dynode, and adeflector l for collecting cathode particles which may be released fromcathode 2 and for bending or defleeting from their normal paths primaryelectrons that pass outwardly through the aperture in the first anode 4so that they may bombard or strike the dynode emitting surface.

Each control electrode 3 is connected to ground through a suitable gridresistor 8. The first anode 4 is connected to a suitable source ofpositive potential as through a'suitable anode resistor 9 and to thegrid or control electrode 3 of the electron'discharge device ll of thesecond stage through as'uitable ,coupling capacitor I2,

2 The junction betweencoupling capacitor I2 and control] electrode 3 is'connected to ground by means of the grid resistor 8 of the next stage,capacitor l2' and resistor 8 being of such values as to. differentiatethe first anodeIpotential.

The dynode or secondelectron emitting electrode isconnectedltoa suitablesource of positive potential as by means of a suitableresistor It. Theauxiliary electrode 6 is connected to a suitable source ofpo'sitivepotential and the deflector. I is connected to. the cathode. Each ofjthedischarge devicesis similarly connected and all the cathodes areconnected together and then to ground through an adjustable resistor l5.

In order to, trigger the counting circuit, there is provided asuitablesource of trigger pulses in dicated by numeral it, these pulsesbeing applied to all of the cathodes through suitable coupling means as,for example, the cathode follower stage indicated by numeral l7. Thetrigger pulses are positive going, i. e., relatively positive withrespect to the base or normal potential.

In operation, as soon as the sources of potential are connected, one ofthe electron discharge devices becomes conductive. Let it be assumedthat device I is conductive. The various potentials and grid bias, aswell as the potential of the positive trigger pulses appearing at theoutput of the source l6, are so chosen that the appearance of the firsttrigger pulse raises the potential of the cathodes sufficiently to out01f the primary stream or fiow of electrons. The potential at anode 4then rises substantially instantaneously to the potential of the anodesupply so that, in effeet, the positive-going pulses are coupled bymeans of coupling capacitor I2 to the grid or control electrode 3 of thenext stage of the ring circuit. The appearance of a sufiicientlypositive potential on grid 3 causes discharge device H to conduct;Conduction in device II results in secondary emission from the dynodewhereupon the potential at the dynode increases rapidly to saturation.The dynode potential is coupled or fed back to the grid circuit by meansof a suitable feedback network including shunt-connected resistor 2i andcapacitor 22, thus providing means intended to maintain grid 3sufiiciently positive after the disappearance of the trigger pulses tomaintain the discharge device I l in a current saturated condition untilthe time of the appearance of the next trigger pulse.

The secondary emission, and hence the development of feedback potential,does not begin until after the driving or trigger pulse substantially sbs des s sa t e J de: mainta ns. g t-oft or nonconductive all tubes ordischarge devices in the circuit. Thereafter, that discharge devicewherein the relative grid-to-cathode potential is most positive fires orbecomes conductive. Since the grid of the next tube in the ring has arelatively higher potential than the other control electrodes because ofthe charge remaining on capacitor l2, the next tube or electrondischarge device fires.

The first anode potential of each discharge device is differentiated inorder to prevent the next 7 pulse from re-triggering the tube which hasjust been conducting instead of triggering on the next tube or electrondischarge device. In order to provide difierentiation, capacitor I2 ischosen to have as small a capacity ,as practicable and, preferably, thecapacity is chosen just large enough to overcome the stray capacitanceof the associated circuits.

Referring to Fig. 2, there is illustrated .at A, typical trigger pulsesrecurring repetitively with equal intervals of time between successivepulses. Curves B, C, and D illustrate the first-anode potentials atdischarge devices I, II, and 23, respectively. These potentialsare lesspositive during the interval when the discharge device is conducting andmore positive when it is nonconducting. Curve E depicts the potential atthe grid or control electrode of each electron discharge device. Dottedline a represents the decreasing potential due to the increase in firstanode potential, i. e., the diiferentiated change in anode potential.Dotted curve b represents the potential appliedto the grid or controlelectrode by the feedback network 2 l22. Inasmuch as the positive-goingtrigger pulses cause the cutting oIT of all discharge devices, theregenerative feedback potential does not begin to build up until thetrigger pulses substantially disappear. The resulting potential at thegrid is represented by the solid line in Fig. 2E. A typical dynodepotential is depicted at Fig. 2F.

The trigger pulse applied to the cathodes need not have sufiicientamplitude actually to cut off the associated discharge devices if theregenerative action in the feedback circuit provides a sufficientlynegative dip when the tube is triggered off, the negative dip beingindicated by the letter e in Fig. 2E.

With the foregoing arrangement only one electron discharge device can beconductive at any one time because with a common cathode resistor, ifmore than one discharge device begins to conduct, an unstable conditionarises wherein the voltage drop across common cathode resistor I5becomes so high that the various electron discharge devices tend to bedriven beyond cut-off.

In the illustrated arrangement, the output leads 2 3 are shown connectedto the first anodesand, as seen in Fig. 2, B, C, and D, negative-goingpulses appear in the output. In order to obtain positive-going pulsesthe output leads may be connected to the dynodes. (See Fig. 2F.)

In a typical circuit employing the principles of my invention, resistors8 were 47,000 ohms, resistors 8 were 10,000 ohms, resistors 2| wereI00,0!l0 ohms, variable resistor I5 was 10,000 ohms, resistors I4 were100,000 ohms, capacitors I2 were '50 micromicrofarads, and capacitors Zlwere l0 micromicrofarads. The trigger pulses had an amplitude ofapproximately 20 volts, a repetition rate of 100 kilocycles and aduration-of approximately half a'microsecond. I

While there has been described what. is at present considered thepreferred embodimentof my invention, it will be obvious to those skilledin the art that various changes and modifications may be made thereinwithout departing from the invention, and it is, therefore, aimed in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of the invention.

What I claim is:

1. In combination, a source of positive-going electric pulses andcircuit means for counting the number of pulses appearing in the outputof said source; said circuit means including a plurality ofinterconnected electron discharge devices; each of said devicescomprising a pair of electrodes between which a primary electron streammay be established, one of said pair of electrodes constituting ananode, a control electrode disposed between said pair of electrodes, andan auxiliary electrode constituting a source of secondary electrons; asource of anode potential; said devices being interconnected such thatonly one of said devices is rendered conductive by the presence of anodepotential in the absence of said positive-going electrical pulses; meansresponsive to the receipt of one of said pulses for establishing primaryand secondary electron streams in another of said devices; and meansresponsive to the flow of secondary electrons in said another deviceforfeeding back from the auxiliary electrode of said another device to thecontrol electrode of said another device potential of such nature as tomaintain said another device conductive after the disappearance of saidone pulse.

2. In combination,.a source of positive-going electric pulses andcircuitmeans for coun ing the number ofpulses appearing in the output ofsaid source; said circuit means including a plurality of interconnectedelectron discharge devices; eachof said devices comprising a pair ofelectrodes between which a primary electron stream may be established,one of said pair of electrodes constituting an anode, a controlelectrode disposed between said pair of electrodes, and an auxiliaryelectrode constituting a source of secondary electrons, a source ofanode potential; said devices being interconnected such that only one ofsaid devices is rendered conductive by the presence of anode potentialin the absence of said positive going electrical pulses; meansresponsive to the receipt of one of said pulses for establishing primaryand secondary electron streams in another of said devices; meansresponsive to the flow of secondary electrons in said another device forfeeding back from the auxiliary electrode of said another device to thecontrol electrode of said another device potential of such natureas tomaintain said another device conductive after the disappearance of saidone pulse; and means responsive to the receipt of the next pulse forrenderingsaid another discharge device non-conductive and still anotherof said discharge devices conductive. v

3. In combination, a source of positive-going electric pulses andcircuit means for counting the number of pulses appearing in the outputof said source; said circuit means including a, plurality ofinterconnected electron discharge devices; each of said devicescomprising a pair of electrodes between which a primary electron streammay be established, one of said pair of electrodes constituting ananode, a control electrode disposed between. said pair of electrodes,and an auxiliary. electrodes constituting a source of secondaryelectrons, a source of anode potential; said devices beinginterconnected such that only one of said devices is rendered conductiveby the presence of anode potential in the absence of said positive-goingelectrical pulses; means responsive to the receipt of one of said pulsesfor establishing primary and secondary electron streams in another ofsaid devices; means responsive to the flow of secondary electrons insaid another device for feeding back from the auxiliary electrode ofsaid another device to the control electrode of said another devicepotential of such nature as to maintain said another device conductiveafter the disappearance of said one pulse, and means utilizing saidfeedpack potential for driving the control electrode of said anotherdevice to a sufliciently low potential with respect to the cathode ofsaid another device at the time of receipt of the next pulse that saidanother discharge device is prevented from again becoming conductive atthe time of receipt of a third pulse.

4. In combination, a source of positive-going electrical pulses andcircuit means for counting the number of pulses appearing in the outputof said source; said circuit means including a plurality ofinterconnected electron discharge devices; each of said devicescomprising a pair of electrodes between which a primary electron streammay be established, an auxiliary electrode constituting a source ofsecondary electrons; one of said pair of electrodes constituting aninput terminal, the other of said pair of electrodes being electricallyconnected to the control electrode of another of said discharge devices;means responsive to the receipt of one of said pulses for establishingprimary and secondary electron streams in said another of said devices;means responsive to the flow of secondary electrons in said anotherdevice for feeding back from the auxiliary electrode of said anotherdevice to the control electrode of said another device pctential of suchnature as to maintain said another device conductive after thedisappearance of said one pulse; and means responsive to the receipt ofthe next pulse for rendering said another discharge device nonconductiveand still another of said discharge devices conductive.

ROBERT B. TROUSDALE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,293,177 Skellett Aug. 18, 19422,309,019 Skellett Jan. 19, 1943 2,404,918 Overbeck July 30, 19462,416,355 Skellett Feb. 25, 1947 2,428,819 Skellett Oct. 14, 1947

